Method and Apparatus for Effecting Automated Movement of a Magnet in an Instrument for Performing a Magnetic Separation Procedure

ABSTRACT

Methods, systems, and apparatus are provided for automated isolation of selected analytes, to which magnetically-responsive solid supports are bound, from other components of a sample. An apparatus for performing an automated magnetic separation procedure includes a mechanism for effecting linear movement of a magnet between operative and non-operative positions with respect to a receptacle device. A receptacle holding station within which a receptacle device may be temporarily stored prior to moving the receptacle to the apparatus for performing magnetic separation includes magnets for applying a magnetic field to the receptacle device held therein, thereby drawing at least a proton of the magnetically-responsive solid supports out of suspension before the receptacle device is moved to the magnetic separation station. An automated receptacle transport mechanism moves the receptacle devices between the apparatus for performing magnetic separation and the receptacle holding station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. 119(e) of U.S.Provisional Application No. 61/178,671, filed May 15, 2009, thedisclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to methods, systems, and apparatus forisolating and separating an analyte of interest (e.g., a target nucleicacid) from other components of a sample.

2. Background of the Invention

All documents referred to herein, or the indicated portions, are herebyincorporated by reference herein. No document, however, is admitted tobe prior art to the claimed subject matter.

Nucleic acid test (NAT) procedures, and other forms of analytedetection, often require a sample preparation procedure for isolatingand separating an analyte from other components of a sample having thepotential to interfere with a test protocol. Many of these samplepreparation procedures require immobilizing analyte onmagnetically-responsive particles, which are then drawn out ofsuspension upon exposure to a magnetic force. The immobilization may bespecific or non-specific for the analyte of interest. Once themagnetically-responsive particles are isolated within a receptacle, thenon-isolated components of the sample may be aspirated and themagnetically-responsive particles resuspended in a fluid medium. Thisprocess can then be repeated one or more times to further purify thesample.

It is desirable, therefore, to have a compact, automated device forperforming the isolation, aspiration and re-suspension steps of a samplepreparation procedure in an analyzer, including structure for removingprotective tips used in the aspiration step.

SUMMARY OF THE INVENTION

Aspects of the invention are embodied in an apparatus which includes afluid transfer device and a slide comprising one or more conduitstripping elements. The fluid transfer device includes one or moreaspirator probes, each aspirator probe having a distal end, and eachdistal end being adapted to have a conduit mounted thereon. Eachstripping element of the slide is associated with a correspondingaspirator probe, and each stripping element is adapted to remove aconduit from the distal end of the associated aspirator probe. The slideis movable between a first position and a second position in theapparatus, such that when the slide is in the first position, nostripping element is in a position to engage the associated aspiratorprobe to strip the conduit mounted thereon, and when the slide is in thesecond position, each stripping element is in a position to engage theassociated aspirator probe to strip the conduit mounted thereon.

In one embodiment, the apparatus further includes one or more magnetscarried by the slide.

In one embodiment, the apparatus further includes a receptacle carrierconfigured to carry a receptacle device in an operative position withrespect to the aspirator probes, and the receptacle carrier isconstructed and arranged to selectively impart an orbital motion to areceptacle device carried by the receptacle carrier.

In one embodiment, the fluid transfer device includes a plurality ofaspirator probes, and the receptacle device includes a plurality ofreceptacles, each receptacle being associated with one of the aspiratorprobes.

In one embodiment, the fluid transfer device further includes a probemoving mechanism adapted to move the plurality of aspirator probes inunison with respect to the associated receptacles.

In one embodiment, the apparatus further includes a guide structure forsupporting the slide for translation between the first and secondpositions and a slide moving mechanism adapted to effect poweredmovement of the slide between the first and second positions.

In one embodiment, the slide moving mechanism includes a motor, athreaded drive screw coupled to an output shaft of the motor, and ascrew follower mounted to the slide. The drive screw is engaged with thescrew follower such that powered rotation of the drive screw by themotor causes translation of the slide.

In one embodiment, the slide moving mechanism includes a motor with adrive pulley mounted to an output shaft thereof, an idler pulley, and adrive belt carried on the drive pulley and the idler pulley and coupledto the slide to transfer powered rotation of the drive pulley totranslation of the slide.

In one embodiment, the apparatus further includes a plurality of theaspirator probes, and the slide comprises a plurality of strippingelements. The stripping elements are arranged in a staggeredconfiguration so that when the plurality of aspirator probes are movedwith respect to the plurality of stripping elements, the strippingelements sequentially remove the conduits from the associated aspiratorprobes one at a time.

Other aspects of the invention are embodied in an apparatus thatincludes a receptacle carrier, a fluid transfer device, and a magnetmoving apparatus. The receptacle carrier is configured to carry areceptacle containing a solution which includes magnetically-responsivesolid supports and to carry the receptacle throughout a fluid transferprocess. The fluid transfer device includes a plurality of aspiratorprobes. The receptacle carrier is constructed and arranged toselectively impart a motion to a receptacle carried by the receptaclecarrier to mix the contents of the receptacle and to selectively movethe receptacle between a first position with respect to the fluidtransfer device and a second position with respect to the fluid transferdevice. The magnet moving apparatus includes at least one magnetgenerating a magnetic field and is constructed and arranged to effectlinear translation of the magnet between an operational position withrespect to the receptacle carried in the receptacle carrier and anon-operational position with respect to the receptacle carried in thereceptacle carrier. The magnetic field draws the magnetically-responsivesolid supports to an inner surface of the receptacle adjacent to themagnet when the at least one magnet is in the operational position, andthe effect of the magnetic field on the magnetically-responsive solidsupports is less when the magnet is in the non-operational position thanwhen the magnet is in the operational position. When the receptacle ispositioned in the first position with respect to the fluid transferdevice, it interferes with translation of the magnet moving apparatusfrom the non-operational position to the operational position.

In one embodiment, the receptacle carrier is constructed and arranged toimpart an orbital motion to the receptacle device carried thereby.

In one embodiment, the fluid transfer device further comprises a probemoving mechanism adapted to move the plurality of probes in unison withrespect to the receptacle carrier. The probe moving mechanism and thereceptacle carrier are constructed and arranged so that movement of theplurality of probes with respect to the receptacle carrier when thereceptacle carrier is in the first position will cause the distal end ofeach probe to engage an associated conduit carried on a receptacledevice carried by the receptacle carrier so that a conduit becomesmounted on the distal end of each probe.

In one embodiment, the magnet moving apparatus comprises a plurality ofstripping elements. Each stripping element is associated with acorresponding aspirator probe, and is adapted to remove a conduit fromthe distal end of the associated aspirator probe. When the magnet movingapparatus is in the operational position, each stripping element is in aposition to engage the associated aspirator probe to strip the conduitmounted thereon, and when the magnet moving apparatus is in thenon-operational position, no stripping element is in a position toengage the associated aspirator probe to strip the conduit mountedthereon.

In one embodiment, the magnet moving apparatus includes a magnet carrierconfigured to carry the magnet, a motor, a threaded drive screw coupledto an output shaft of the motor, and a screw follower mounted to themagnet carrier. The drive screw is engaged with the screw follower suchthat powered rotation of the drive screw by the motor causes translationof the magnet carrier.

In one embodiment, the magnet moving apparatus includes a magnet carrierconfigured to carry the magnet, a motor with a drive pulley mounted toan output shaft thereof, an idler pulley, and a drive belt carried onthe drive pulley and the idler pulley and coupled to the magnet carrierto transfer powered rotation of the drive pulley to translation of themagnet carrier.

Further aspects of the invention are embodied in a method for removing aconduit from a distal end of each of a plurality of fluid transferprobes. A slide is moved by powered translation in a directiontransverse to the axes of the probes from a first location to a secondlocation. When the slide is in the first location, no portion of theslide is in a position to be engaged by any of the probes, and when theslide is in the second location, conduit-stripping portions of the slideare in positions to be engaged by the distal ends of the probes. Withthe slide in the second position, the probes are moved axially withrespect to the slide to engage the distal ends of the probes with theconduit-stripping portions of the slide to strip the conduits from theprobes.

In one embodiment, stripping the conduits from the distal ends of theprobes includes moving the probes in an axial direction toward the slideuntil the conduits disposed on the distal ends of the probes engage theconduit-stripping portions of the slide and then moving the probes in anopposite axial direction away from the slide while retaining theconduits with the conduit-stripping portions of the slide to pull theconduits from the distal ends of the probes.

In one embodiment, retaining the conduits with the conduit-strippingportions of the slide providing, for each conduit-stripping portion, akey-hole opening having a first portion with a transverse sizesufficient to permit the conduit to pass therethrough and a secondportion with a transverse size sufficient to permit the probe to passtherethrough, but not sufficient to permit the conduit to passtherethrough;. The distal end of the probe with the conduit disposedthereon is passed through the first portion of the key-hole opening.Relative movement between the probe and the slide is effected so thatthe probe is in the second portion of the key-hole opening. The probe isthen withdrawn from the key-hole opening while the conduit is retainedby the conduit-stripping portion when the conduit is unable to passthrough the second portion of the key-hole opening.

In one embodiment, each of the conduits is sequentially retained duringaxial movement of the probes away from the slide so that all conduitsare not pulled from the distal ends of the probes simultaneously.

In one embodiment, one or more magnets is mounted on the slide suchthat, when the slide is in the first location, the magnets havesubstantially no effect on magnetically-responsive solid supportscontained in a receptacle device positioned so as to be engageable bythe probes, and when the slide is in the second location, the magnetsare positioned adjacent to the receptacle device so that the magnetswill draw at least a portion of the magnetically-responsive solidsupports to a wall of the receptacle device.

In one embodiment, the magnetically-responsive solids supports areadapted to immobilize an analyte thereon.

Other aspects of the invention are embodied in a system for separatingan analyte of interest from other components of a sample contained in areceptacle. The system includes a receptacle holding station and amagnetic separation station. The receptacle holding station isconfigured to receive and hold a receptacle delivered to the receptacleholding station by a receptacle transport and includes one or morestationary magnets positioned to apply a magnetic field to the contentsof the receptacle held in the receptacle holding station. The magneticseparation station comprises one or more magnets and is constructed andarranged to perform a magnetic separation procedure on the contents of areceptacle transported from the receptacle holding station to themagnetic separation station by a receptacle transport by magneticallyisolating an analyte immobilized on a magnetically-responsive solidsupport and removing other components of the sample from the receptacle.

In one embodiment, the system further includes a receptacle transportconfigured to automatically move the receptacle between the receptacleholding station and the magnetic separation station.

In one embodiment, the receptacle holding station is configured toreceive and hold a receptacle device comprising a plurality ofindividual receptacles.

In one embodiment, the receptacle holding station is configured toreceive and hold at least two receptacle devices.

In one embodiment, the receptacle holding station includes a base block,two or more walls extending upwardly from the base block, and a shroudpartially covering the two or more walls and defining a receptacle slotbetween each adjacent pair of walls. In one embodiment, the receptacleholding station comprises a first wall, a second wall, and a third wallextending upwardly from the base block and defining a first receptacleslot between the first and second walls and a second receptacle slotbetween the second and third walls.

In one embodiment, the base block of the receptacle holding station ismade from plastic.

In one embodiment, the receptacle holding station further includes aresilient receptacle retaining element within each receptacle slot andconfigured to releasably retain a receptacle within each receptacleslot.

In one embodiment, each of the resilient receptacle retaining elementsincludes a clip disposed within a clip recess formed in one wall of eachpair of walls defining a receptacle slot.

In one embodiment, the receptacle holding station further includes amagnet subassembly attached to one wall of each pair of walls defining areceptacle slot. The magnet subassembly includes a plurality of magnets,an upper holder plate disposed within holder plate grooves formed withinthe top surface of each of the magnets and which includes a separatingprojection at each end thereof and between adjacent magnets to hold eachmagnet within its respective position, and a lower holder plate disposedwithin holder plate grooves formed in the lower surfaces of the magnetsand which includes a separating projection at opposite ends thereof andbetween the adjacent magnets to hold each magnet within its respectiveposition.

In one embodiment, each of the magnets has a generally solid,rectangular shape.

In one embodiment, the magnetic separation station includes a magnetmoving apparatus constructed and arranged to move the one or moremagnets between a first position in which the magnets have substantiallyno effect on the magnetically-responsive solid supports contained withinthe receptacle and a second position in which the magnets cause thesolid supports to become isolated within the receptacle.

Other aspects of the invention are embodied in a method for separatingan analyte of interest from other components of a sample contained in areceptacle. At a first location, a receptacle containingmagnetically-responsive solid supports dispersed in a fluid mediumcomprising a sample material is exposed to a first magnetic field,thereby isolating the solid supports within the receptacle. The solidsupports are adapted to immobilize an analyte thereon. The receptacle isthen transferred to a second location. At the second location, thecontents of the receptacle are subjected to a second magnetic field,thereby isolating the solid supports within the receptacle, the fluidcontents of the receptacle are removed from the isolated solid supports,the second magnetic field is then removed, a suspension fluid isdispensed into the receptacle, and the solid supports are re-suspended.

In one embodiment, steps occurring at the second location are repeatedone or more times.

In one embodiment, after repeating the steps one or more times, thereceptacle is removed from the second location.

In one embodiment, the first location comprises a receptacle holdingstation configured to receive and hold the receptacle and includes oneor more stationary magnets constructed and arranged to apply the firstmagnetic field to the contents of the receptacle held in the receptacleholding station

In one embodiment, the second location comprises a magnetic separationstation constructed and arranged to perform a magnetic separationprocedure on the receptacle by positioning magnets to magneticallyisolate the magnetically-responsive solid support and then removing thefluid medium from the receptacle.

In one embodiment, the transferring step comprises withdrawing thereceptacle from the first location with an automated receptacletransport, carrying the receptacle with the receptacle transport fromthe first location to the second location, and depositing the receptacleat the second location with the receptacle transport.

In one embodiment, the solid supports remain substantially isolatedwithin the receptacle during the transfer from the first location to thesecond location.

These and other features, aspects, and advantages of the presentinvention will become apparent to those skilled in the art afterconsidering the following detailed description, appended claims andaccompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a reaction receptacle in the form of amultiple receptacle device employed in combination with an apparatusembodying aspects of the present invention;

FIG. 2 is a side elevation of a contact-limiting tip employed incombination with an instrument for performing a magnetic separationprocedure and carried on the multiple receptacle device shown in FIG. 1;

FIG. 3 is an enlarged bottom view of a portion of the multiplereceptacle device, viewed in the direction of arrow “60” in FIG. 1;

FIG. 4 is a perspective view of a magnetic separation station with aside plate thereof removed;

FIG. 5 is a partial transverse cross-section of the magnetic separationstation;

FIG. 6 is a partial transverse cross-section of a tip of an aspiratortube of the magnetic separation station with a contamination-limitingtip carried on the end thereof;

FIG. 7 is an exploded perspective view of a receptacle carrier unit, anorbital mixer assembly, and a divider plate of the magnetic separationstation;

FIG. 8 is a partial cross-sectional view of a wash solution dispensernozzle, an aspirator tube with a contamination-limiting tip engaged withan end thereof, and a receptacle carrier unit of the magnetic separationstation, showing a multiple receptacle device reaction receptaclecarried in the receptacle carrier unit and the aspirator tube andcontamination-limiting tip inserted into a receptacle of the multiplereceptacle device;

FIG. 9 is a partial cross-sectional view of the wash solution dispensernozzle, the aspirator tube, and the receptacle carrier unit of themagnetic separation station, showing the multiple receptacle devicecarried in the receptacle carrier unit and the aspirator tube engagingthe contamination-limiting tip held in a contamination-limiting elementholding structure of the multiple receptacle device;

FIG. 10 is a top perspective view of a portion of a magnetic separationstation illustrating an alternate embodiment of a magnet movingapparatus;

FIG. 11 is a partial perspective view the magnet moving apparatus ofFIG. 10;

FIG. 12 is a partial perspective view of a magnetic separation stationillustrating a further alternate embodiment of a magnet movingapparatus;

FIG. 13 is a top perspective view of a magnet sled of the magnet movingapparatus of FIG. 12;

FIG. 14 is a bottom perspective view of the magnet sled of FIG. 13;

FIG. 15 is a top view of the magnet sled of FIGS. 13 and 14.

FIG. 16 is a front perspective view of a magnetic receptacle holdingstation for reaction receptacles.

FIG. 17 is a rear perspective view of the magnetic receptacle holdingstation.

FIG. 18 is a partial front perspective of the receptacle holding stationwith various components of the receptacle holding station omitted fromthe figure.

FIG. 19 is a perspective view of a magnet subassembly of the magneticreceptacle holding station.

FIG. 20 is a perspective view of a receptacle transfer apparatus in theform of a receptacle distributor suitable for use in conjunction withembodiments of the present invention.

FIG. 21 is a perspective view of the receptacle distribution head and ahook actuator system in an extended position.

FIG. 22 is a flow chart illustrating a procedure for separating orisolating an analyte of interest (e.g., a target nucleic acid) fromother components of a sample employing magnets andmagnetically-responsive solid supports.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Samples often include or are treated to release materials capable ofinterfering with the detection of an analyte (e.g., a targeted nucleicacid). To remove these interfering materials, samples can be treatedwith a target capture reagent that includes a magnetically-responsivesolid support for immobilizing the analyte. See, e.g., U.S. Pat. Nos.4,486,539, 4,751,177, 5,288,609, 5,780,224, 6,433,160, and 6,534,273.Suitable solid supports are paramagnetic particles (0.7-1.05 micronparticles, Sera-Mag™ MG-CM, available from Seradyn, Inc., Indianapolis,Ind., as Cat. No. 24152105-050450) with covalently bound oligo(dT)₁₄.When the solid supports are brought into close proximity to a magneticforce, the solid supports are drawn out of suspension and aggregateadjacent a surface of a sample holding container, thereby isolating anyimmobilized analyte within the container. Non-immobilized materials inthe sample can then be aspirated or otherwise separated from immobilizedanalyte. One or more wash steps may be performed to further purify theanalyte.

Methods, systems, and apparatus for performing a procedure for isolatingand separating an analyte of interest from other components of a sampleare embodied in a magnetic separation station, an embodiment of which isshown in FIG. 4. The magnetic separation station comprises a housingconfigured to receive a reaction receptacle which contains a samplematerial and a target capture reagent including magnetically-responsivesolid supports adapted to directly or indirectly bind to an analyte ofinterest, such as a nucleic acid, that may be present in the sample.Details of an exemplary reaction receptacle and sample preparationprocedures are described in more detail below.

The magnetic separation station includes magnets for attracting themagnetically-responsive solid supports to a side wall of the reactionreceptacle and apparatus for selectively moving the magnets between afirst position in which the magnets have substantially no effect on themagnetically-responsive solid supports contained within the reactionreceptacle and a second position in which the magnets draw themagnetically-responsive solid supports to a side wall of the reactionreceptacle. In particular embodiments, the apparatus for selectivelymoving the magnets is configured to effect a linear translation of themagnets between the first and the second positions. Such an apparatusmay comprise a sled on which the magnets are carried and which may beactuated for linear translation by a belt or a threaded rod driven by amotor. The magnetic separation station further includes apparatus foraspirating fluids from a reaction receptacle held in the station,apparatus for dispensing fluids into the reaction receptacle, andapparatus for agitating the reaction receptacle to re-suspendmagnetically-responsive solid supports and other materials following theaspirating and dispensing steps. The apparatus for aspirating fluidsfrom the reaction receptacles may include aspirator tubes, and removableprotective tips may be placed on the ends of the aspirator tubes andexchanged for new tips after each reaction receptacle is processed bythe magnetic separation station to prevent contamination from onereaction receptacle to the next. The apparatus for effecting linearmovement of the magnets may include tip removal elements adapted forremoving the tips from the aspirator tubes after each receptacle isprocessed by the magnetic separation station.

A reaction receptacle containing sample material and a target capturereagent that includes magnetically-responsive solid supports is placedinto the magnetic separation station, and the magnets are moved from thefirst, non-affecting position to the second position adjacent to thereaction receptacle. The magnets are held in the second position for aspecified dwell time to draw magnetically-responsive solid supports tothe side of the reaction receptacle. After the specified dwell time,with the magnets still in the second position, the fluid contents of thereaction receptacle are aspirated from the receptacle. A wash solutionor other suspending fluid is then dispensed into the reactionreceptacle, the magnets are moved back to the first position, and thereaction receptacle is agitated to rinse the magnetically-responsivesolid supports from the reaction receptacle wall and re-suspend themagnetically-responsive solid supports. The magnets are then moved backto the second position to draw the magnetically-responsive solidsupports to the walls of the reaction receptacle and out of suspension.This process of applying a magnetic force for a specified dwell time,aspirating fluid from the reaction receptacle, and re-suspending themagnetically-responsive solid supports may be repeated a specifiednumber of times.

The magnetic separation station may be part of an instrument includingvarious modules configured to receive one or more reaction receptacleswithin which is performed one or more steps of a multi-step analyticalprocess, such as a nucleic acid test (NAT), or other chemical,biochemical or biological process. The instrument may further include atransfer apparatus configured to transfer reaction receptacles betweenthe various modules, including transporting reaction receptacles intoand out of the magnetic separation station. The instrument and eachindividual component, such as the magnetic separation station, isautomated and may be controlled by an instrument control moduleincluding a microprocessor executing an instrument control programstored thereon.

Further details of the magnetic separation station are described below.

Other aspects of the invention are embodied in a magnetic receptacleholding station, an embodiment of which is shown in FIG. 16. Thereceptacle holding station comprises a structure configured forreceiving and temporarily holding a reaction receptacle in a stationaryposition. The receptacle holding station includes magnets configured soas to be positioned adjacent to the reaction receptacle when thereceptacle is held within the receptacle holding station. A reactionreceptacle containing sample material to which magnetically-responsivesolid supports have been added can be placed into the receptacle holdingstation for a specified dwell time prior to moving the reactionreceptacle into the magnetic separation station. Themagnetically-responsive solid supports will be drawn to the side wall ofthe reaction receptacle to form an aggregate of solid supports prior tothe receptacle being placed in the magnetic separation station, thusreducing at least the first magnetic dwell time required within themagnetic separation station.

Further details of the magnetic receptacle holding station are describedbelow.

Multiple Receptacle Devices

As shown in FIG. 1, a reaction receptacle in the form of a multiplereceptacle device (“MRD”) 160 that can be used in conjunction with themagnetic separation station and the magnetic receptacle holding stationof the present invention comprises a plurality of individual receptacles162, preferably five. Other types of receptacle devices can be used inconjunction with the magnetic separation and magnetic receptacle holdingstations, including devices comprising a single, individual receptacle.In the illustrated embodiment, the receptacles 162 are in the form ofcylindrical tubes with open top ends and closed bottom ends and areconnected to one another by a connecting rib structure 164 which definesa downwardly facing shoulder extending longitudinally along either sideof the MRD 160. In the illustrated embodiment of the MRD 160, all of thereceptacles 162 are substantially identical in size and shape. In otherembodiments, the MRD 160 may include receptacles of varying sizes andshapes, which can be configured for use with the magnetic separation andmagnetic receptacle holding stations.

In one embodiment, the MRD 160 is formed from injection moldedpolypropylene, such as that manufactured by Flint Hills Resources asproduct number P5M6K-048.

An arcuate shield structure 169 is provided at one end of the MRD 160.An MRD manipulating structure 166 extends from the shield structure 169.The manipulating structure is adapted to be engaged by a transportmechanism for moving the MRD 160 between different locations or modulesof an instrument. Exemplary transport mechanisms that are compatiblewith the MRD 160 are described in U.S. Pat. No. 6,335,166 and in U.S.Provisional Application No. 61/178,728 and corresponding non-provisionalU.S. application Ser. No. 12/781,241. MRD manipulating structure 166comprises a laterally extending plate 168 extending from shieldstructure 169 with a vertically extending piece 167 on the opposite endof the plate 168. A gusset wall 165 extends downwardly from lateralplate 168 between shield structure 169 and vertical piece 167.

As shown in FIG. 3, the shield structure 169 and vertical piece 167 havemutually facing convex surfaces. The MRD 160 may be engaged by atransport mechanism and other components, by moving an engaging memberlaterally (in the direction “A”) into the space between the shieldstructure 169 and the vertical piece 167. The convex surfaces of theshield structure 169 and vertical piece 167 provide for wider points ofentry for an engaging member undergoing a lateral relative motion intothe space.

A label-receiving structure 174 having a flat label-receiving surface175 is provided on an end of the MRD 160 opposite the shield structure169 and MRD manipulating structure 166. Human and/or machine-readablelabels, such as scanable bar codes, can be placed on the surface 175 toprovide identifying and instructional information on the MRD 160.

The MRD 160 preferably includes tip holding structures 176 adjacent theopen mouth of each respective receptacle 162. Each tip holding structure176 provides a cylindrical orifice within which is received a conduit,such as contact-limiting tip 170, that is adapted to be placed onto theend of an aspirator tube 860. The construction and function of the tip170 will be described below. Each holding structure 176 can beconstructed and arranged to frictionally receive a tip 170 in a mannerthat prevents the tip 170 from falling out of the holding structure 176when the MRD 160 is inverted, but permits the tip 170 to be removed fromthe holding structure 176 when engaged by an aspirator tube 860.

As shown in FIG. 2, the tip 170 comprises a generally cylindricalstructure having a peripheral rim flange 177 and an upper collar 178 ofgenerally larger diameter than a lower portion 179 of the tip 170. Thetip 170 is preferably formed from conductive polypropylene. When the tip170 is inserted into an orifice of a holding structure 176, the flange177 contacts the top of structure 176 and the collar 178 provides a snugbut releasable interference fit between the tip 170 and the holdingstructure 176. Alternatively, each holding structure 176 may beconfigured to loosely receive a tip 170 so that the tip 170 is moreeasily removed from the holding structure when engaged by an aspiratortube 860.

An axially extending through-hole 180 passes through the tip 170. Hole180 includes an outwardly flared end 181 at the top of the tip 170 whichfacilitates insertion of a tubular probe (not shown) into the tip 170.Two annular ridges 183 may be provided on the inner wall of hole 180.Ridges 183 provide an interference friction fit between the tip 170 anda tubular probe inserted into the tip 170.

The bottom end of the tip 170 preferably includes a beveled portion 182.When tip 170 is used on the end of an aspirator tube 860 that isinserted to the bottom of a reaction receptacle, such as a receptacle162 of an MRD 160, the beveled portion 182 prevents a vacuum fromforming between the end of the tip 170 and the bottom of the reactionreceptacle.

Further details regarding the MRD 160 may be found in U.S. Pat. No.6,086,827.

Specimen Preparation Procedure

For nucleic acid tests, it may be necessary to lyse or permeabilizecells to first release a targeted nucleic acid and make it available forhybridization with a detection probe. See, e.g., Clark et al., “Methodfor Extracting Nucleic Acids from a Wide Range of Organisms,” U.S. Pat.No. 5,786,208. If the cells are lysed, the contents of the resultinglysate may include, in addition to nucleic acids, organelles, proteins(including enzymes such as proteases and nucleases), carbohydrates, andlipids, which may necessitate further purification of the nucleic acids.Additionally, for pathogenic organisms, chemical or thermal inactivationof the organisms may be desirable. Cells may be lysed or permeabilizedby a variety of means well known to those skilled in the art, includingby chemical, mechanical (e.g., sonication) and/or thermal means.

Various methods for capturing nucleic acids usingmagnetically-responsive solid supports are known in the art and can beemployed in the present invention. These methods may be specific ornon-specific for the targeted nucleic acid. One such method is SolidPhase Reversible Immobilization, which is based on the selectiveimmobilization of nucleic acids onto magnetic microsolid support havingcarboxyl group-coated surfaces. See U.S. Pat. No. 5,705,628. In anothermethod, magnetic particles having poly(dT) sequences derivatized thereonbind to capture probes having 5′ poly(dA) tails and 3′ target bindingsequences. See U.S. Pat. No. 6,534,273. Still another approach is basedon the ChargeSwitch® Technology, which is a magnetic bead-basedtechnology that provides a switchable surface that is charge dependenton the surrounding buffer pH to facilitate nucleic acid purification(Invitrogen Corporation, Carlsbad, Calif.; Cat. No. CS12000). In low pHconditions, the ChargeSwitch® Magnetic Beads have a positive charge thatbinds the negatively charged nucleic acid backbone. Proteins and othercontaminants that are not bound can be washed away. By raising the pH to8.5, the charge on the surface is neutralized and the bound nucleicacids are eluted.

For approaches involving capture probes, the capture probes may bespecific or non-specific for the targeted nucleic acids. A specificcapture probe includes a target binding region that is selected to bindto a target nucleic acid under a predetermined set of conditions and notto non-target nucleic acids. A non-specific capture probe does notdiscriminate between target and non-target nucleic acids under theconditions of use. Wobble capture probes are an example of anon-specific capture probe and may include at least one random ornon-random poly(K) sequence, where “K” can represent a guanine, thymineor uracil base. See U.S. Patent Application Publication No. US2008-0286775 A1. In addition to hydrogen bonding with cytosine, itspyrimidine complement, guanine will also hydrogen bond with thymine anduracil. Each “K” may also represent a degenerate nucleoside such asinosine or nebularine, a universal base such as 3-nitropyrrole,5-nitroindole or 4-methylindone, or a pyrimidine or purine base analogsuch as dP or dK. The poly(K) sequence of a wobble capture probe is ofsufficient length to non-specifically bind the target nucleic acid, andis preferably 6 to 25 bases in length.

Sample material is prepared for a magnetic separation procedure bydispensing a specified amount of a target capture reagent into eachsample-holding receptacle of a receptacle device. Dispensing may beperformed manually or by an automated, robotic pipetting apparatus—intoeach of the receptacles 162 of the MRD 160. The target capture reagentincludes a solid support material able to directly or indirectly bind toan analyte, such as through a capture probe, thereby immobilizing theanalyte on the solid support comprises magnetically-responsive particlesor beads. The amount dispensed into each receptacle 162 is typically inthe range of 100-500 μL.

Magnetic Separation Stations

Turning to FIGS. 4-5, a magnetic separation station 800 includes amodule housing 802 having an upper section 801 and a lower section 803.Mounting flanges 805, 806 extend from the lower section 803 for mountingthe magnetic separation station 800 to a support surface by means ofsuitable mechanical fasteners. Locator pins 807 and 811 extend from thebottom of lower section 803 of housing 802. Pins 807 and 811 registerwith apertures (not shown) formed in the support surface to help tolocate the magnetic separation station 800 on the support surface beforethe housing 802 is secured by fasteners.

A loading slot 804 extends through the front wall of the lower section803 to allow a transport mechanism (not shown) to place a receptacledevice, such as an MRD 160, into and remove the receptacle device fromthe magnetic separation station 800. A tapered slot extension 821 may beprovided around a portion of the loading slot 804 to facilitatereceptacle insertion through the slot 804. A divider 808 separates theupper section 801 from the lower section 803.

A receptacle carrier unit 820 is disposed adjacent the loading slot 804,below the divider 808, for operatively supporting the receptacledisposed within the magnetic separation station 800. For purposes ofillustration, the receptacle carrier unit 820 is shown in FIG. 5carrying an MRD 160, but other receptacles, including single, individualreceptacles and multiple receptacle devices having receptacles ofvarying shapes and sizes, may be used. Turning to FIG. 7, the receptaclecarrier unit 820 has a slot 822 for receiving the upper end of areceptacle device, such as an MRD 160. In the illustrated embodiment, alower fork plate 824 attaches to the bottom of the receptacle carrierunit 820 and supports the underside of the connecting rib structure 164of the MRD 160 when slid into the carrier unit 820 (see FIGS. 8 and 9).A spring clip 826 is attached to the carrier unit 820 with its opposedprongs 831, 833 extending into the slot 822 to releasably hold thereceptacle within the carrier unit 820.

As an alternative to the arrangement shown in FIG. 7, the receptaclecarrier unit 820 may comprise a single, injection molded part, which mayinclude an integrally-formed ledge if configured for supporting an MRD160, and an integrally-formed plastic spring element for retaining areceptacle within the receptacle carrier unit 820.

An orbital mixer assembly 828 is coupled to the carrier unit 820 fororbitally mixing the contents of an MRD, or other receptacle device,held by the receptacle carrier unit 820. The orbital mixer assembly 828includes a stepper motor 830 mounted on a motor mounting plate 832, adrive pulley 834 having an eccentric pin 836, an idler pulley 838 havingan eccentric pin 840, and a belt 835 connecting drive pulley 834 withidler pulley 838. A suitable stepper motor includes a VEXTA, modelnumber PK245-02A, available from Oriental Motors Ltd. of Tokyo, Japan,and suitable belts 835 include a timing belt, model number A6G16-170012, available from SDP/SI of New Hyde Park, N.Y. As shown inFIGS. 5 and 7, eccentric pin 836 fits within a slot 842 formedlongitudinally in the receptacle carrier unit 820. Eccentric pin 840fits within a circular aperture 844 formed in the opposite end ofreceptacle carrier unit 820. As the motor 830 turns the drive pulley834, idler pulley 838 also rotates via belt 835 and the receptaclecarrier unit 820 is moved in a horizontal orbital path by the eccentricpins 836, 840 engaged with the apertures 842, 844, respectively, formedin the carrier unit 820. The rotation shaft 839 of the idler pulley 838preferably extends upwardly and has a transverse slot 841 formedtherethrough. An optical slotted sensor 843 is disposed at the samelevel as the slot 841 and measures the frequency of the idler pulley 838via the sensor beam intermittently directed through slot 841 as theshaft 839 rotates. A suitable sensor includes an Optek Technology, Inc.,model number OPB980T11, sensor, available from Optek Technology, Inc. ofCarrollton, Tex.

As an alternative to slot 841 and sensor 843, the frequency of idlerpulley 838 may be measured by means of an encoder (not shown) mounted onthe top of shaft 839.

Drive pulley 834 also includes a locator plate 846. Locator plate 846passes through slotted optical sensors 847, 848 mounted to a sensormounting bracket 845 extending from motor mounting plate 832. Suitablesensors include Optek Technology, Inc., model number OPB980T11, sensors,available from Optek Technology, Inc. of Carrollton, Tex. Locator plate846 has a plurality of circumferentially spaced axial openings formedtherein which register with one or both sensors 847, 848 to indicate aposition of the orbital mixer assembly 828, and thus a position of thereceptacle carrier unit 820.

As an alternative to locator plate and sensors 847, 848, the frequencyand position of drive pulley 834 may be measured by means of an encoder(not shown) coupled to the pulley 834.

A pivoting magnet moving apparatus 810 is attached inside the lowersection 803 so as to be pivotable about point 812. The magnet movingapparatus 810 carries permanent magnets 814, which are positioned oneither side of a slot 815 formed in the magnet moving apparatus 810. Themagnet moving apparatus 810 is constructed and arranged to move themagnets 814 between an operational position and a non-operationalposition with respect to a receptacle device carried in the receptaclecarrier unit 820. In the operational position, the magnets 814 aredisposed adjacent the receptacle, e.g., the MRD 160, and in sufficientproximity to the receptacle so that magnetically-responsive solidsupports within each receptacle 162 are drawn out of suspension by theattraction of the magnetic fields of the magnets 814. In thenon-operational position, the magnets are disposed at a sufficientdistance from the receptacles 162 so as to have no substantial effect onthe contents of the receptacles 162. In the present context, “nosubstantial effect” means that the magnetically-responsive solidsupports are not drawn out of suspension by the attraction of themagnetic fields of the magnets 814.

Preferably five magnets, one corresponding to each individual receptacle162 of the MRD 160, are held in an aligned arrangement on each side ofthe magnet moving apparatus 810. The magnets are preferably made ofneodymium-iron-boron (NdFeB), minimum grade n-35 and have preferreddimensions of 0.5 inch width, 0.3 inch height, and 0.3 inch depth. Anelectric actuator, generally represented at 816, pivots the magnetmoving apparatus 810 up and down, thereby moving the magnets 814. Asshown in FIG. 5, actuator 816 preferably comprises a rotary steppermotor 819 which rotates a drive screw mechanism coupled to the magnetmoving apparatus 810 to selectively raise and lower the magnet movingapparatus 810. Motor 819 is preferably an HSI linear stepper actuator,model number 26841-05, available from Haydon Switch and Instrument, Inc.of Waterbury, Conn.

A sensor 818, preferably an optical slotted sensor, is positioned insidethe lower section 803 of the housing for indicating the down, or “home”,or non-operational, position of the magnet moving apparatus 810. Anothersensor 817, also preferably an optical slotted sensor, is preferablyprovided to indicate the up, or operational, position of the magnetmoving apparatus 810. Suitable sensors include model number OPB980T11,available from Optek Technology, Inc. of Carrollton, Tex.

An alternate embodiment of a magnet moving apparatus for moving themagnets between operational and non-operational positions with respectto the receptacle is shown in FIGS. 10 and 11. The magnet movingapparatus comprises magnet slide 200 which comprises a magnet sled 202that is moved along a linear path by a drive system 232.

More specifically, the magnet sled 202 includes a first wall 204 havinga guide rod aperture 206 and a rectangular, U-shaped cutout 208. The amagnet sled 202 further comprises a second wall 214 having a guide rodaperture 216 and a rectangular cutout 218 formed therein. A first magnet220 is positioned between the first wall 204 and the second wall 214 onone side of the respective cutouts 208, 218 and is supported by a firstmagnet backing plate 224. Similarly, a second magnet 222 is disposedbetween the first wall 204 and the second wall 214 on an opposite sideof the respective rectangular cutouts 208, 218 and is backed by a magnetbacking plate (not shown). Magnets 220, 222 may be made from NdFeB,grade n-35 or grade n-40. As an alternative to single magnets 220, 222on opposite sides of the magnet sled 202, individual magnets may beprovided on each side of the sled 202, one for each receptacle 162. Inone embodiment, the sled includes five magnets on each side, each magnethaving a size of approximately 12 mm×12 mm×7.5 mm and being made fromNdFeB, grade n-40. The number of magnets corresponds to the number ofreceptacles 162 comprising the MRD 160.

Magnet sled 202 further includes a bottom plate 226 with a plurality oftip stripping elements in the form of stripping openings 228 formedtherein. Operation of the tip stripping openings 228 will be describedbelow. Finally, the magnet sled 202 includes a guide surface formed inpart by a straight laterally extended edge 230 formed in the first wall204. A similar laterally extending straight edge is formed in the backwall 214. Any of the first and second walls 204, 214, first and secondmagnet backing plates 224, and bottom plate 226 may be integrally formedwith each other. Suitable materials for the first and second walls 204,214 and bottom plate 226 include non-magnetically-responsive materialssuch as plastics and aluminum. Preferred material for the first andsecond magnet backing plates 224 include magnetically-responsivematerials, such as steel, to increase magnetic flux flowing through themagnets.

The drive system 232 comprises a drive motor 234 having a drive pulley236 and mounted on the outside of the lower housing 803. A drive belt238 is carried on the drive pulley 236 and an idler pulley 248 andextends through an opening 813 formed in the lower housing 803. Oppositeends 243, 245 of the drive belt 238 are attached to the magnet sled 202by means of a coupling bracket 240. Suitable belts are available fromthe Gates Corporation.

The coupling bracket 240 includes a top plate 241 disposed across thetop of the second magnet 222 and having belt retaining slots withinwhich opposite ends 243, 245 of the drive belt 238 are inserted andsecured. A retainer tab 247 bent transversely with respect to the topplate 241 is positioned within a conforming slot formed in the firstwall 204. A similar tab (not shown) is provided on the opposite end ofthe top plate 241 and extends within a conforming slot formed in thesecond wall 214 for securing the coupling bracket 240 to the magnet sled202.

The magnet sled 202 is disposed inside the lower housing 803 with theguide surface 230 supported on a guide ledge 242 extending along aninner surface of the lower housing 803. The opposite side of the magnetsled 202 is supported by a guide rod 212 extending across the lowerhousing 803 and through the guide rod apertures 206 and 216. A bushing(not shown) may be provided at either or both of the guide rod apertures206, 216 for securely and slidably supporting the magnet sled 202.

Rotation of the drive pulley 236 by the drive motor 234 turns the drivebelt 238 to thereby move the magnet sled 202 between a non-operationalposition, such as shown in FIGS. 10 and 11, and an operational positionwhereby the magnet sled 202 is moved to the opposite side of the lowerhousing 803. When the magnet sled 202 is moved to the operationalposition, the lower ends of the receptacles 162 pass through therectangular cutouts 208, 218 of the first wall 204 and second wall 214,respectively, so as to be disposed between the first magnet 220 and thesecond magnet 222.

A retracted position sensor 244 mounted to an inner surface of the lowerhousing 803 indicates when the magnet sled 202 is in a retracted, ornon-operational, position. Similarly, an extended position sensor 246,also mounted to an inner surface of the lower housing 803, indicateswhen the magnet sled 202 is in an extended, or operational, position.Sensors 244 and 246 may comprise slotted optical sensors which detectthe presence of a tab (not shown) projecting from a lower portion of themagnet slide 202.

A further alternative embodiment of a magnet moving apparatus is shownin FIGS. 12-15. The magnet moving apparatus of FIGS. 12-15 comprises amagnet slide 250 including a magnet sled 252 and a drive system 284which moves the magnet sled 252 between a non-operational position (asshown in FIG. 12) and an operational position with respect to anreceptacle.

More specifically, the magnet sled 252 comprises a first wall 254including a screw follower 256 and a rectangular opening 258. Anextended flange 260 may be provided around the rectangular opening 258.The magnet sled 252 further comprises a second wall 262 having a guidebushing 264 and a rectangular opening 266. A first magnet 268 isdisposed between the first wall 254 and the second wall 262 and issupported by a first magnet backing plate 272. Similarly, a secondmagnet 270 is disposed between the first wall 254 and the second wall262 on an opposite side of the rectangular openings 258, 266 and issupported by a second magnet backing plate 274. Again, as an alternativeto single magnets 268, 270 on opposite sides of the magnet sled 252,five individual magnets having a size of approximately 12 mm×12 mm×8 mmand made from NdFeB, grade n-40 can be provided on each side of the sled252.

The magnet sled 252 further includes a bottom plate 276 in which aplurality of tip stripping openings 278 are formed, a guide surface 280,and a retainer bracket 282. Guide surface 280 may comprise two surfacesdisposed on opposite sides of the retainer bracket 282.

A drive system 284 includes a drive motor to a 286 mounted on theexterior of the lower housing 803 and having a drive pulley 288. Athreaded drive screw 292 extends across the lower housing 803 and isjournaled at its opposite ends to the lower housing wall so as to berotatable about its longitudinal axis. Threaded drive screw 292 furtherincludes a pulley 294 located at one end thereof. The threaded drivescrew 292 is operatively coupled to the drive motor 286 by means of adrive belt 290 carried on the drive pulley 288 of the drive motor 286and the pulley 294 of the threaded drive screw 292.

The threaded drive screw 292 extends through the screw follower 256 ofthe first wall 254 and the guide bushing 264 of the second wall 262. Theguide surface 280 on the bottom surface of the magnet sled 252 andlocated on the opposite side of the sled 252 from the screw follower 256and guide bushing 264 slidably rests on a guide flange 295 extendingalong an inner wall of the lower housing 803. A lower portion of theretainer bracket 282 extends beneath the guide flange 295 so that theguide flange is disposed between the guide surface 280 and the retainerbracket 282.

Rotation of the drive pulley 288 by the drive motor 286 is transferredto the threaded drive screw 292 by means of the drive belt 290. Therotating drive screw 292 engaged with the screw follower 256 causeslinear translation of the magnet sled 252 in a longitudinal directionwith respect to the drive screw 292. Rotation of the drive screw 292 inone direction will cause left to right translation of the magnet sled252, and rotation of the screw 292 in the opposite direction will causeright to left translation of the magnet sled 252. The retainer bracket282 engaged with the underside of the guide flange 295 prevents themagnet sled 252 from tipping out of contact with the guide flange 295due to friction between the drive screw 292 and the screw follower 256.

When the magnet sled 252 is moved from the non-operational position,shown in FIG. 12, to an operational position, the receptacle passesthrough the rectangular openings 258, 266 and is disposed between thefirst magnet 268 and second magnet 270. The extended flange 260 formedaround the rectangular opening 258 of the first wall 254 will assist inguiding the receptacle through the opening 258.

A retracted position sensor 296 mounted to the inner wall of the lowerhousing 803 indicates when the magnet sled 252 is in a retracted, ornon-operational, position, and an extended position sensor 298, alsomounted to the inner wall of the lower housing 803, indicates when themagnet sled 252 is in an extended, or operational, position with respectto the receptacle. Sensors 296 and 298 may comprise optical sensorswhich detect the presence of a tab extending from a portion of themagnet sled 252.

Returning to FIG. 4, wash solution delivery tubes 854 connect tofittings 856 and extend through a top surface of the module housing 802.Wash solution delivery tubes 854 extend through the divider 808 viafittings 856, to form a wash solution delivery network.

As shown in FIGS. 8 and 9, wash solution dispenser nozzles 858 extendingfrom the fittings 856 are disposed within the divider 808. Each nozzleis located above a respective receptacle 162 of the MRD 160 at alaterally off-center position with respect to the receptacle 162. Eachnozzle includes a laterally-directed lower portion 859 for directing thewash solution into the respective receptacle 162 from the off-centerposition. Suitable wash solutions are known to those skilled in the art,an example of which contains 10 mM Trizma base, 0.15 M LiCl, 1 mM EDTA,and 3.67 mM lithium lauryl sulfate (LLS), at pH 7.5. Dispensing fluidsinto the receptacles 162 in a direction having a lateral component canlimit splashing as the fluid runs down the sides of the respectivereceptacles 162. In addition, the laterally directed fluid can rinseaway materials clinging to the sides of the respective receptacles 162.

As shown in FIGS. 4 and 5, aspirator tubes 860, or probes, extendthrough a tube holder 862, to which the tubes 860 are fixedly secured,and extend through openings 861 in the divider 808. A tip sense printedcircuit board (“PCB”) 809 (see FIG. 7) is attached by mechanicalfasteners to the side of divider 808, below openings 861. Aspiratorhoses 864 connected to the aspirator tubes 860 extend to a vacuum pump(not shown), with aspirated fluid drawn off into a fluid waste containercarried (not shown). In one embodiment, each of the aspirator tubes 860has a length of 12 inches with an inside diameter of 0.041 inches.

The tube holder 862 is attached to a drive screw 866 actuated by a liftmotor 868. A suitable lift motor includes the VEXTA, model numberPK245-02A, available from Oriental Motors Ltd. of Tokyo, Japan, and asuitable drive screw includes the ZBX series threaded anti-backlash leadscrew, available from Kerk Motion Products, Inc. of Hollis, N.H. In theillustrated embodiment, the tube holder 862 is attached to a threadedsleeve 863 of the drive screw 866. Rod 865 and slide rail 867 functionas a guide for the tube holder 862. Alternatively, a linear bearing (notshown) may be employed as a guide for the tube holder 862. Z-axissensors 829, 827 (slotted optical sensors) cooperate with a tabextending from the tube holder 862 and/or the threaded sleeve 863 toindicate top and bottom of stroke positions of the aspirator tubes 860.Suitable Z-axis sensors include Optek Technology, Inc., model numberOPB980T11, sensors, available from Optek Technology, Inc. of Carrollton,Tex. Together, the tube holder 862, lift motor 868, and drive screw 866comprising an embodiment of a moving mechanism for the tubes 860.

Cables bring power and control signals to the magnetic separationstation 800, via one or more connectors (one such connector is shown atreference number 870).

The magnet moving apparatus 810, 200, 250 is initially in anon-operational position (e.g., as shown in phantom in FIG. 5 and inFIGS. 10 and 12), as verified by the retracted position sensor 818, 244,296, when the receptacle is inserted into the magnetic separationstation 800 through the insert opening 804 and into the receptaclecarrier unit 820. When the magnet moving apparatus is in thenon-operational position, the magnetic fields of the magnets will haveno substantial effect on the magnetically-responsive solid supportscontained in the receptacle. The orbital mixer assembly 828 moves thereceptacle carrier unit 820 a portion of a complete orbit so as to movethe receptacle carrier unit 820 and MRD 160 laterally, so that each ofthe tips 170 carried by the tip holding structures 176 of the MRD 160 isaligned with each of the aspiration tubes 860, as shown in FIG. 9. Theposition of the receptacle carrier unit 820 is verified, for example, bythe locator plate 846 and one of the sensors 847, 848. Alternatively,the stepper motor 830 can be moved a known number of steps to place thereceptacle carrier unit 820 in the desired position, and one of thesensors 847, 848 can be omitted. Note that magnet moving apparatuscannot move to an operational position when the receptacle carrier unit820 has been moved to this tip engagement position because the MRD 160carried by unit 820 will interfere with movement of the magnet movingapparatus.

The tube holder 862 and aspirator tubes 860 are lowered by the liftmotor 868 and drive screw 866 until each of the aspirator tubes 860frictionally engages a conduit, e.g., a tip 170, held in an associatedcarrying structure 176 on the MRD 160.

As shown in FIG. 6, the lower end of each aspirator tube 860 ischaracterized by a tapering, step construction, whereby the tube 860 hasa first portion 851 along most of the extent of the tube, a secondportion 853 having a diameter smaller than that of the first portion851, and a third portion 855 having a diameter smaller than that of thesecond portion 853. The diameter of the third portion 855 is such as topermit the end of the tube 860 to be inserted into the flared portion181 of the through-hole 180 of the tip 170 and to create an interferencefriction fit between the outer surface of third portion 855 and aportion of the inner wall of the through-hole 180, such as the twoannular ridges 183 (see FIG. 2) or alternatively,longitudinally-oriented ridges (not shown), that line the inner wall ofhole 180 of tip 170. An annular shoulder 857 is defined at thetransition between second portion 853 and third portion 855. Theshoulder 857 limits the extent to which the tube 860 can be insertedinto the tip 170, so that the tip can be stripped off after use, as willbe described below.

The tips 170 may be at least partially electrically conductive, so thatthe presence of a tip 170 on an aspirator tube 860 can be verified bythe capacitance of a capacitor comprising the aspirator tubes 860 andtips 170 as one half of the capacitor and the surrounding hardware ofthe magnetic separation station 800 (e.g., the metal divider 808) as theother half of the capacitor. A suitable resin for forming the tips 170is available from Fiberfil® Engineered Plastics Inc. as product numberPP-61/EC/P BK, which is a carbon filled conductive polypropylene. Asdetermined by the tip sense PCB 809, the capacitance will change whenthe tips 170 are engaged with the ends of the aspirator tubes 860.

In addition to, or as an alternative to capacitive tip sensing, fiveoptical slotted sensors (not shown) can be strategically positionedabove the divider 808 to verify the presence of a tip 170 on the end ofeach aspirator tube 860. Suitable “tip-present” sensors include OptekTechnology, Inc., model number OPB930W51, sensors, available from OptekTechnology, Inc. of Carrollton, Tex. A tip 170 on the end of anaspirator tube 860 will break the beam of an associated sensor to verifypresence of the tip 170. If, following a tip pick-up move, tipengagement is not verified by the tip present sensors for all fiveaspirator tubes 860, an error signal will be generated. The MRD 160 maybe aborted, and the aborted MRD 160 will be retrieved from the magneticseparation station 800 and ultimately discarded, or processing maycontinue in the receptacle(s) 162 corresponding to aspirator tube(s) 860for which tip presence is successfully verified

After successful conduit engagement, the orbital mixer assembly 828moves the receptacle carrier unit 820 back to a fluid transfer positionshown in FIG. 8 as verified by the locator plate 846 and one or both ofthe sensors 847, 848.

The magnet moving apparatus 810, 200, 250 is then moved to theoperational position (e.g., as shown in FIG. 4) so that the magnets aredisposed adjacent opposite sides of the receptacle, such as MRD 160.With the contents of the receptacle subjected to the magnetic fields ofthe magnets, the magnetically-responsive solid supports having targetednucleic acids immobilized thereon will be drawn to the sides of theindividual receptacles 162 adjacent the magnets. The remaining materialwithin the receptacles 162 should be substantially unaffected, therebyisolating the target nucleic acids. The magnet moving apparatus willremain in the operational position for an appropriate dwell time, asdefined by the assay protocol and controlled by the assay managerprogram, to cause the magnetic solid supports to adhere to the sides ofthe respective receptacles 162. In one embodiment, the distance betweenthe opposed magnets on opposite sides of the magnet moving apparatus isabout 12.4 mm and the diameter of each receptacle 162 of MRD 160 is 11.4mm, which means there is a gap of 0-1 mm between the magnet and the sideof the receptacle 162 when the magnet moving apparatus is in theoperational position. When the magnet moving apparatus is moved to thenon-operational position, there is a clearance of at least 30 mm betweenthe magnets and the receptacles 160.

The aspirator tubes 860 are then lowered into the receptacles 162 of theMRD 160 to aspirate the fluid contents of the individual receptacles162, while the magnetic solid supports remain in the receptacles 162,aggregated along the sides thereof, adjacent the magnets. The tips 170at the ends of the aspirator tubes 860 ensure that the contents of eachreceptacle 162 do not come into contact with the sides of the aspiratortubes 860 during the aspirating procedure. Because the tips 170 will bediscarded before a subsequent MRD 160 is processed in the magneticseparation station 800, the chance of cross-contamination by theaspirator tubes 860 is minimized.

The electrically conductive tips 170 can be used in a known manner forcapacitive fluid level sensing within the receptacles 162 of the MRDs160. The aspirator tubes 860 and the conductive tips 170 comprise onehalf of a capacitor, the surrounding conductive structure within themagnetic separation station comprises the second half of the capacitor,and the fluid medium between the two halves of the capacitor constitutesthe dielectric. Capacitance changes due to a change in the nature of thedielectric can be detected.

The capacitive circuitry of the aspirator tubes 860 can be arranged sothat all five aspirator tubes 860 operate as a single gang level-sensingmechanism. When any of the aspirator tubes 860 and its associated tip170 contacts fluid material within a receptacle 162, capacitance of thesystem changes due to the change in the dielectric. If the Z-position ofthe aspirator tubes 860 at which the capacitance change occurs is toohigh, then a high fluid level in at least one receptacle 162 isindicated, thus implying an aspiration failure or overdispense. On theother hand, if the Z-position of an aspirator tube 860 at which thecapacitance change occurs is correct, but one or more of the other tubeshas not yet contacted the top of the fluid due to a low fluid level, alow fluid level will be indicated.

Alternatively, the aspirator tube capacitive circuitry can be arrangedso that each of the five aspirator tubes 860 operates as an individuallevel sensing mechanism.

With five individual level sensing mechanisms, the capacitive levelsensing circuitry can detect failed fluid aspiration in one or more ofthe receptacles 162 if the fluid level in one or more of the receptacles162 is high. Individual capacitive level sensing circuitry can detectfailed fluid dispensing into one or more of the receptacles 162 if thefluid level in one or more of the receptacles 162 is low. Furthermore,the capacitive level sensing circuitry can be used for volumeverification to determine if the volume in each receptacle 162 is withina prescribed range. Volume verification can be performed by stopping thedescent of the aspirator tubes 860 at a position above expected fluidlevels, e.g. 110% of expected fluid levels, to make sure none of thereceptacles 162 has a level that high, and then stopping the descent ofthe aspirator tubes 860 at a position below the expected fluid levels,e.g. 90% of expected fluid levels, to make sure that each of thereceptacles 162 has a fluid level at least that high.

Following aspiration, the aspirator tubes 860 are raised, the magnetmoving apparatus moves to the non-operational position, the receptaclecarrier unit 820 is moved to the fluid dispense position (FIG. 9), and aprescribed volume of wash solution is dispensed into each receptacle 162of the MRD 160 through the wash solution dispenser nozzles 858. Toprevent hanging drops of wash solution on the wash solution dispensernozzles 858, a brief, post-dispensing air aspiration is preferred.

The orbital mixer assembly 828 then moves the receptacle carriers 820 ina horizontal orbital path at high frequency (in one embodiment, 14 HZ,accelerating from 0 to 14 HZ in 1 second) to mix the contents of thereceptacle. Mixing by moving, or agitating, the MRD 160 in a horizontalplane is preferred so as to avoid splashing the fluid contents of thereceptacle and to avoid the creation of aerosols. Following mixing, theorbital mixer assembly 828 stops the receptacle carrier unit 820 at thefluid transfer position.

To further purify the targeted nucleic acids, the magnet movingapparatus 810, 200, 250 is again moved to the operational position andmaintained in the operational position for a prescribed dwell period.After magnetic dwell, the aspirator tubes 860 with the engaged tips 170are lowered to the bottoms of the receptacles 162 of the MRD 160 toaspirate the test specimen fluid and wash solution in an aspirationprocedure essentially the same as that described above.

One or more additional wash cycles, each comprising a dispense, mix,magnetic dwell, and aspirate sequence, may be performed as defined bythe assay protocol. Those skilled in the art of NATs will be able todetermine the appropriate magnetic dwell times, number of wash cycles,wash solutions, etc. for a desired target capture procedure.

Multiple magnetic separation stations 800 can be employed in aninstrument to permit separation wash procedures to be performed onmultiple MRDs 160 in parallel. The number of magnetic separationstations 800 will vary depending on the desired throughput of theinstrument.

After the final wash step, the magnet moving apparatus 810, 200, 250 ismoved to the non-operational position, and the MRD 160 is removed fromthe magnetic separation station 800 by a transport mechanism. Prior toremoving the MRD 160 from the magnetic separation station 800, andpreferably prior to magnet retraction, a final residual volume check maybe performed by lowering the aspirator tubes 860 and tips 170 to aposition just above the bottom of each receptacle 162 to determine ifany excess fluid volume remains in the receptacle 162.

After the MRD 160 is removed from the magnetic separation station 800,the tips 170 are stripped from the aspiration tubes 860 by the tipstripping openings 228, 278.

The magnet sled 202 of the magnet slide 200 shown in FIG. 10 and themagnet sled 252 of the magnet slide 250 shown in FIG. 12 both includetip stripping openings 228, 278, respectively, formed along a centralportion of a lower surface thereof between the first and second magnets.The tip stripping openings, as shown in FIG. 15, comprise keyhole shapeopenings having a first portion 279 and a second portion 277, with thefirst portion 279 being larger than the second portion 277. The numberof tip stripping openings is equal to the number of aspirator tubes 860,which, in the illustrated embodiment, is five.

To strip the conduits, or tips 170, off of each of the aspirator tubes860, the magnet sled 202, 252 is positioned beneath the aspirator tubes860 so that the larger portions 279 of the tip stripping openings 278are aligned with each of the aspirator tubes 860. The aspirator tubes860, with the tips 170 disposed thereon, are lowered through the firstportions 279 of the stripping openings, which are large enough to permitthe tips 170 to pass therethrough. After the tips 170 have passedthrough the tip stripping openings, the magnet sled is moved slightly sothat the aspirator tubes 860 are disposed within the second, smallerportions 277 of the stripping openings, which are large enough toaccommodate the aspirator tubes 860, but are smaller than the outsidediameter of the rim flange 177 of the tips 170. The aspirator tubes 860are then raised, and the tips 170 engage the peripheral edgessurrounding the second portion 277 of the stripping openings, therebypulling the tips 170 off of the aspirator tubes 860 as the aspiratortubes 860 ascend. Preferably, the tip stripping openings are disposed atstaggered vertical locations so that as the aspirator tubes 860 areraised in unison, the tips 170 encounter the peripheral edges of thestripping openings in a staggered manner. For example, each strippingopening may be at a different vertical position, so that as theaspirator tubes 860 are moved with respect to the stripping openings,the tips 170 are sequentially removed from the associated aspiratortubes 860 one at a time. One benefit of staggering the strippingopenings is that it results in smaller forces being exerted on themoving mechanism defined by the tube holder 862, lift motor 868, anddrive screw 866.

Although operation of the magnetic separation station 800 was previouslydescribed primarily in conjunction with an MRD 160, the inventiveaspects of the magnetic separation station 800 is not limited to its usewith an MRD 160 as other types of receptacles, including singlereceptacles and multiple receptacle devices, including receptacles ofvarying sizes, can be processed in a magnetic separation stationembodying aspects of the present invention.

Magnetic Receptacle Holding Stations

The magnetic receptacle holding station and various components thereofare shown in FIGS. 16-19. As shown in FIGS. 16 and 17, a magneticreceptacle holding station 300 includes a base block 310 with a firstwall 330, second wall 360, and third wall 368 secured to and, extendingupwardly from the base block 310, and a shroud 370 partially coveringthe first, second, and third walls 330, 360, 368. A first receptacleslot 356 defined between first and second walls 330, 360 and a secondreceptacle slot 358 defined between second and third walls 360, 368 areeach configured to receive an MRD 160, or other receptacle, as shown inFIG. 16. As shown in FIG. 18—in which the second wall 360, third wall368, and shroud 370 are omitted—the base block 310 includes mountingflanges 312 for securing the receptacle holding station 300 to a datumplate, outer wall grooves 314, 316 for securing the first wall 330 andthird wall 368, respectively, and a center slot 318 within which issecured the second wall 360. Base block 310 and walls 330, 360, 368 maybe made from a suitable plastic, such as Delrin® acetal resin or PVC.

A grounding connector element 322 is secured to one of the mountingflanges 312.

Referring to FIG. 18, first wall 330 includes a magnet slot 332 formedtherein along a lower portion thereof and a clip slot 334 formed thereinalong an upper portion thereof. A magnet subassembly 338 is mountedwithin the magnet slot 332 by mechanical fasteners, such as screws. Aclip element 352 is mounted within the clip slot 334. A hook accesscorner cutout 354 is provided in the upper front corner of the firstwall 330. Third wall 368 is substantially a mirror image of first wall330 and includes a magnet slot within which a magnet subassembly ismounted and a clip slot within which a clip is mounted. In theillustrated embodiment, third wall 368 does not include a hook accesscutout. Second wall 360 includes a magnet slot 362 within which a magnetsubassembly 364 is mounted. A partial corner hook access cutout 366 isprovided at the upper front portion of the second wall 360.

Shroud 370 includes a top panel 372, side panels 374, and a back panel376 (see FIG. 17). Shroud 370 may be formed from an suitable material,such as sheet metal. Shroud 370 is secured to the first and third walls330, 368, and a grounding connector 320 is secured to one side 374 ofthe shroud 370.

Referring to FIG. 19, the magnet subassembly includes a plurality ofmagnets 340 (five in the illustrated embodiment), each being of agenerally solid rectangular shape. An upper holder plate 344 is disposedwithin holder plate grooves 342 formed within the top surface of each ofthe magnets 340. Upper holder plate 344 includes a separating projection346 at each end thereof and between adjacent magnets 340 to hold eachmagnet within its respective position. Similarly, the magnet subassembly338 includes a lower holder plate 348 which is received within holderplate grooves formed in the lower surfaces of the magnets 340 and whichincludes a separating projection 350 at opposite ends thereof andbetween the adjacent magnets 340.

A receptacle, such as an MRD 160, can be placed within the receptacleholding slot 356 or 358 and supported on the upper edges 336 of theopposed first and second walls or second and third walls. Clip 352,which may comprise a resilient projection extending into the slot 356,releasably secures the MRD 160 within the slot. The hook access cutouts354, 366 permit a manipulating hook (not shown) to be positionedalongside the manipulating structure 166 of the MRD 160 and to engagethe manipulating structure 166 in the direction A as shown in FIG. 3.

An MRD 160 containing a sample material and a target capture reagentincluding magnetically-responsive solid supports can be placed withinone of the slots 356, 358 of the magnetic receptacle holding station300, and retained therein for a specified dwell time while themagnetically-responsive solid supports are drawn out of solution by themagnets of the magnetic receptacle holding station 300. After thespecified dwell time, the MRD 160 is moved from the magnetic receptacleholding station 300 to the magnetic separation station 800. By placingthe MRDs 160 into the magnetic receptacle holding station 300 for aspecified dwell time prior to moving the MRDs 160 into the magneticseparation station 800, the amount of magnetic dwell time required inthe magnetic separation station 800 can be reduced, thereby reducing theamount of time that each MRD 160 must spend in the magnetic separationstation 800 and improving overall instrument throughput.

A magnetic receptacle holding station 300 shown in FIGS. 16-18 is forillustration purposes only. It should be recognized that a receptacleholding station embodying aspects of the present invention may have lessthan or more than three upright walls and two receptacle holding slotsdefined between opposed walls.

Transport Mechanism

An embodiment of a transport mechanism suitable for moving a receptacle,such as the MRD 160, into and out of the magnetic separation station 800and the magnetic receptacle holding station 300 and between the magneticseparation station 800 and the magnetic receptacle holding station 300will now be described.

As shown in FIG. 20, a receptacle transfer apparatus in the form of areceptacle distributor 400 comprises a receptacle carrier assembly 402which translates along a transport track assembly 408 in an “X”direction” under the power of an X-translation system (described below).The receptacle carrier assembly 402 includes a receptacle distributionhead 404 configured to carry a reaction receptacle, such as an MRD 160,supported on a carrier assembly carriage 418 constructed and arranged toeffect Z-axis translation and Θ rotation of the distribution head 404.In the illustrated embodiment, the track assembly 408 is linear (i.e.,straight) and substantially horizontal, but in other embodiments, thetrack assembly is non-linear (i.e., at least partially curved) and/ornon-horizontal (i.e., at least a portion of the track assembly isinclined or vertical).

In the illustrated embodiment, track assembly 408 comprises a generally“L” shaped channel 424 comprising a base portion 434—orientedsubstantially horizontally in the illustrated embodiment—and an uprightbacking 440 extending in an upright manner—oriented substantiallyvertically in the illustrated embodiment—from one edge of the horizontalbase 434. A stiffening flange 430 extends upright from an edge of thebase portion 434 opposite the upright backing 440, and a stiffeningflange 442 extends laterally from an upper edge of the upright backing440. A guide rail 446 is mounted to the upright backing 440 and extendsin a parallel orientation with respect to the base portion 434. A cableguide track 432 is mounted to the base portion 434.

An X-translation system 410 comprises a drive, or transmission, belt 448trained over a driven pulley 412 disposed on one side of the uprightbacking 440 at a distal end 414 of the channel 424 and over an idlerpulley 436 disposed on the same side of the upright backing 440 at aproximal end 428 of the channel 424 and attached at opposite endsthereof to the carrier assembly carriage 418. Driven pulley 412 isoperatively coupled to a carrier translation motor (not shown) mountedto an opposite side of the upright backing 440. A rotational encoder(not shown) is coupled to the drive motor.

The drive belt 448 is preferably equipped with a belt tensioner 438.Belt tensioner 438 comprises a sliding pulley mount, on which is mountedthe idler pulley 436, and a spring. The pulley mount is slidablysupported by the upright backing 440, but can be selectively fixed withrespect to the upright backing 440 by a fastener element to preventsliding of the mount. The spring urges the pulley mount inbelt-tightening direction when the pulley mount 436 is not fixed withrespect to the upright backing 440.

The distribution head 404 of the carrier assembly 402 is carried alongthe transport track assembly 408 by the carrier assembly carriage 418.The carrier assembly carriage 418 engages the guide rail 446, andtranslates along the transport track assembly 408. Rubber bumpers 444,406 may be provided at opposite ends of the guide rail 446 to absorbcontact by the carriage 418. Movement of the carrier assembly carriage418 along the guide rail 446 is effected by the drive belt 448. When thecarrier translation motor rotates the driven pulley 412 in acounter-clockwise fashion, the carrier assembly 402 is moved in a firstX direction (to the left in the illustrated embodiment) towards theproximal end 428 of transport track assembly 408. Similarly, when thecarrier translation motor rotates driven pulley 412 in a clockwisefashion, the carrier assembly 402 translates in a second X direction (tothe right in the illustrated embodiment) towards the distal end 414 oftransport track 408 assembly.

Details of the distribution head 402 are shown in FIG. 21. Distributionhead 402 includes a distribution frame 454 that is supported forrotation about a vertical axis of rotation by the carrier assemblycarriage 418. A side panel 488 is attached to one side of thedistribution head frame 454. Side panel 488 may be transparent so thatthe interior of the distribution head 402 is visible. Distribution head402 further includes a receptacle hook 500 configured to engage themanipulating structure 166 of an MRD 160. Devices other than a hook forengaging the receptacle and enabling physical manipulation of theengaged receptacle may be substituted.

A hook actuator system 456 effects linear translation (in the Rdirection relative to the Z-axis and the Θ direction) of the receptaclehook 500 between an extended position, as shown in FIG. 21, and aretracted position in which the MRD 160 is withdrawn into thedistribution head 402. The hook actuator system 456 includes a hookcarriage 480 to which the receptacle hook 500 is attached. A drive belt486 is attached to the hook carriage 480 by a screw and bracketindicated at 490. Drive belt 486 is carried on a drive wheel 462 andidler wheels 464, 496, 452, 458. Idler wheels 452 and 458 are attachedto a fixed idler wheel bracket 460, and idler wheel 496 is attached toan upper portion of a door engagement bracket 494 exterior to panel 488.

Door engagement bracket 494 may be provided for opening a door coveringthe loading slot 804. The door, which may be a pivoting, sliding, orrotating door, will include an arm or other projection depending from aportion of the door. In one embodiment, the distribution head 402 ispositioned with the lower end of the door engagement bracket 494 incontact with the arm, and a slight X and/or Θ movement of thedistribution head 402 is effected to move the door from a closed to anopen position. The door is preferably spring-biased in a closedposition, so that that when the arm is released from contact with thedoor engagement bracket 494, the door will spring back to the closedposition.

Drive wheel 462 is attached to an output shaft of a drive motor(notshown) (preferably a stepper motor) which is mounted to an opposite sideof the distribution frame 454. A rotational encoder (not shown) isattached to the drive motor. Drive wheel 462 preferably has a diameterof 9.55 mm resulting in a resolution of 0.15 mm per full motor step. Theencoder had a resolution of 200 counts/revolution (A-B signals)resulting in a quadrupled resolution of 800 counts/revolution.

The hook actuator system 456 preferably includes a belt tensioner 476for maintaining proper tension in the belt 486. Belt tensioner 476includes a pivoting idler wheel bracket 474 to which idler wheel 464 isattached and which is pivotally attached to the side panel 488 by apivot screw 478. A slot 470 is formed in an end of the pivoting idlerwheel bracket 474, and a position lock screw 468 extends through theslot 470 into the side panel 488. A spring 472 is disposed between aportion of the pivoting idler wheel bracket 474 and the fixed idlerwheel bracket 460. Tension in the belt 486 can be adjusted by looseningthe position lock screw 468, thereby allowing the spring 472 to pivotthe pivoting idler wheel bracket 474 and thus urge the idler wheel 464upwardly to create the proper tension in the drive belt 486. When propertension is achieved in the drive belt 486, the position lock screw 468can thereafter be retightened.

The hook carriage 480 includes a rail channel 484 that translates alonga hook carriage guide rail 450 attached to an upper portion of thedistribution head frame 454. The receptacle hook 500 is attached to aninsulation mount 498 disposed between the rail channel 484 and the hook500 to electrically isolate the hook 500 from the distribution head 402to facilitate capacitive sensing of contact by the hook 500 with anotherstructural element of, e.g., the magnetic separation station 800 or thereceptacle holding station 300.

Further details of the receptacle distributor can be found in U.S.Patent Application No. 61/178,728, the disclosure of which isincorporated by reference.

A procedure for separating or isolating an analyte of interest, such asa target nucleic acid, from other components of a sample is representedby process 510 shown in FIG. 22. The process begins at step 512 with aspecimen preparation procedure whereby sample specimen and a targetcapture reagent including magnetically-responsive solid supports areadded to a receptacle device (a single receptacle or multiplereceptacles, e.g., the MRD 160). The sample specimen and target capturereagent may be added to the receptacle device by any means known in theart, including manual and automated means.

In step 514, the receptacle device containing the sample specimen andtarget capture reagent is subjected to conditions sufficient to causethe analyte of interest to be immobilized on the magnetically-responsivesolid support. The conditions may include incubation of the receptacledevice and its contents at one or more prescribed temperatures forprescribed periods of time. Procedures for immobilizing targeted nucleicacids on magnetically-responsive solid supports are exemplified in U.S.Pat. No. 6,534,273 and U.S. Patent Application Publication No.2008-0286775.

In step 516, a decision is made as to whether to (1) move the receptacledevice to a magnetic receptacle holding station 300 prior to moving thereceptacle device to the magnetic separation station 800 or (2) move thereceptacle device directly into a magnetic separation station 800.

If the decision is made to omit placing the receptacle device in themagnetic receptacle holding station 300, then, in step 526, thereceptacle device is placed in the magnetic separation station 800,preferably using a receptacle transport mechanism, such as receptacledistributor 400 described above.

In step 530, with the receptacle device supported by the receptaclecarrier unit 820 of the magnetic separation station 800, the receptaclecarrier unit 820 is positioned to align each aspirator tube 860 with atip 170 carried on the receptacle device, and each aspirator tube 860 islowered until it is inserted into and frictionally engages a tip 170. Inalternative embodiments, the tips are not carried on the receptacledevice but are otherwise provided to each aspirator tube 860.

In step 532, magnets, which are initially in an inoperative positionwith respect to the receptacle device when the receptacle device isfirst placed into the magnetic separation station 800 in step 526, aremoved to an operative position with respect to the receptacle device todraw magnetically-responsive solid supports toward the side of thereceptacle device. In step 534, the receptacle device is held stationaryin the receptacle carrier unit 820 with the magnets in an operativeposition for a specified dwell period (in one embodiment, 120 seconds)sufficient to draw a substantial portion of the magnetically-responsivesolid supports to the side wall of the receptacle device and out ofsuspension.

In step 536, after performing a procedure to verify the presence of atip 170 on each aspirator tube 860, the receptacle carrier unit 820 ismoved to position each receptacle below an associated aspirator tube860, each aspirator tube 860 is lowered into the associated receptacle,and fluid is aspirated from the receptacle in step 536, preferably whilethe magnets are maintained in the operative position with respect to thereceptacle device.

In step 538, the magnets are moved to a non-operative position withrespect to the receptacle device so that the magnetically-responsivesolid supports of the target capture reagent will not be influenced bythe magnetic force of the magnets.

In step 540, a wash solution is dispensed into each receptacle (e.g., 1mL of wash buffer), and, in step 542, the receptacle device is agitatedto dislodge the magnetically-responsive solid supports from the walls ofthe receptacle device and to re-suspend the magnetically-responsivesolid supports.

In step 544, a decision is made as to whether additional wash steps mustbe performed. Depending on the procedure protocol, the wash proceduremay be repeated one or more times. In one embodiment, 2 wash cycles areperformed. If the wash procedure is to be repeated, the process returnsto step 532, and steps 532 through 542 are repeated. If no further washsteps are to be performed, the receptacle device is removed from themagnetic separation station 800 in step 546.

In step 548, the tip 170 is stripped from each aspirator tube 860, andthe magnetic separation station 800 is now ready to receive the nextreceptacle device to perform the magnetic separation wash process.

If, at step 516, the decision was made to place the receptacle device inthe receptacle holding station 300 prior to moving it to the magneticseparation station 800, in step 518 the receptacle device is placed inthe receptacle holding station 300, preferably using a receptacletransport mechanism, such as receptacle distributor 400 described above.

In step 520, the receptacle device is allowed to sit in the magneticreceptacle holding station 300 for a specified dwell period (in oneembodiment, 580 seconds) sufficient to draw a substantial portion of themagnetically-responsive solid supports to the walls of the receptacledevice and out of suspension.

In step 522, after the specified dwell period, and assuming theavailability of a magnetic separation station 800, the receptacle deviceis moved from the receptacle holding station 300 to the magneticseparation station 800, using, for example, the receptacle distributor400 described above. In one embodiment, the transfer from the receptacleholding station 300 to the magnetic separation station occurs in 4seconds.

In step 524, each aspirator tube 860 is engaged with a tip 170 asdescribed above in connection with step 530.

In step 528, magnets, which are initially in an inoperative positionwith respect to the receptacle device when the receptacle device isfirst placed into the magnetic separation station 800 in step 522, aremoved to an operative position with respect to the receptacle device. Asthe magnetically-responsive solid supports of the target capture probecontained in the receptacle device have already been subjected to amagnetic force for a specified dwell period within the magneticreceptacle holding station 300 in step 520, an initial magnetic dwellperiod within the magnetic separation station 800 can be substantiallyshortened, or omitted altogether. That is, if the contents of thereceptacle device are not agitated, a substantial portion of the solidsupports will remain aggregated to the side of the receptacle devicewhile the receptacle device is transferred from the receptacle holdingstation to the magnetic separation station. In experiments, theinventors have determined that the initial magnetic dwell can be reducedby 180 seconds by use of the magnetic receptacle holding station 300(initial dwell of 300 seconds without first placing the receptacledevice in the magnetic receptacle holding station as compared to 120second initial magnetic dwell when the receptacle device is first placedin the magnetic receptacle holding station for 580 seconds).

The process next proceeds to step 536, and fluid is aspirated from thereceptacle device while the magnetically-responsive solid supports areheld to the walls of the receptacle device by the magnets. The processthen proceeds through steps 540 through 548 as describedabove—returning, as desired, to step 532 to repeat steps 532-542.

While the present invention has been described and shown in considerabledetail with reference to certain illustrative embodiments, those skilledin the art will readily appreciate other embodiments of the presentinvention. Accordingly, the present invention is deemed to include allmodifications and variations encompassed within the spirit and scope ofthe following appended claims.

1. An apparatus comprising: a fluid transfer device comprising one ormore aspirator probes, each aspirator probe having a distal end, andeach distal end being adapted to have a conduit mounted thereon; a slidecomprising one or more conduit-stripping elements, each strippingelement being associated with a corresponding aspirator probe, and eachstripping element being adapted to remove a conduit from the distal endof the associated aspirator probe, wherein the slide is movable betweena first position and a second position in the apparatus, such that whenthe slide is in the first position, no stripping element is in aposition to engage the associated aspirator probe to strip the conduitmounted thereon, and when the slide is in the second position, eachstripping element is in a position to engage the associated aspiratorprobe to strip the conduit mounted thereon.
 2. The apparatus of claim 1,further comprising one or more magnets carried by the slide.
 3. Theapparatus of claim 1, further comprising a receptacle carrier configuredto carry a receptacle device in an operative position with respect tothe aspirator probes, wherein the receptacle carrier is constructed andarranged to selectively impart an orbital motion to a receptacle devicecarried by the receptacle carrier.
 4. The apparatus of claim 3, whereinthe fluid transfer device comprises a plurality of aspirator probes, andwherein the receptacle device comprises a plurality of receptacles, eachreceptacle being associated with one of the aspirator probes.
 5. Theapparatus of claim 4, wherein said fluid transfer device furthercomprises a probe moving mechanism adapted to move the plurality ofaspirator probes in unison with respect to the associated receptacles.6. The apparatus of claim 1, further comprising a guide structure forsupporting said slide for translation between said first and secondpositions and a slide moving mechanism adapted to effect poweredmovement of said slide between said first and second positions.
 7. Theapparatus of claim 6, wherein said slide moving mechanism comprises: amotor; a threaded drive screw coupled to an output shaft of said motor;and a screw follower mounted to said slide, wherein said drive screw isengaged with said screw follower such that powered rotation of saiddrive screw by said motor causes translation of said slide.
 8. Theapparatus of claim 6, wherein said slide moving mechanism comprises: amotor with a drive pulley mounted to an output shaft thereof; an idlerpulley; and a drive belt carried on said drive pulley and said idlerpulley and coupled to said slide to transfer powered rotation of saiddrive pulley to translation of said slide.
 9. An apparatus of claim 1,comprising a plurality of said aspirator probes, and wherein said slidecomprises a plurality of stripping elements, and wherein the strippingelements are arranged in a staggered configuration so that when theplurality of aspirator probes are moved with respect to the plurality ofstripping elements, the stripping elements sequentially remove theconduits from the associated aspirator probes one at a time.
 10. Anapparatus comprising: a receptacle carrier configured to carry areceptacle device containing a solution which includesmagnetically-responsive solid supports and to carry the receptacledevice throughout a fluid transfer process; a fluid transfer devicecomprising a plurality of aspirator probes; wherein said receptaclecarrier is constructed and arranged to selectively impart a motion to areceptacle device carried by said receptacle carrier to mix the contentsof the receptacle device and to selectively move the receptacle devicebetween a first position with respect to said fluid transfer device anda second position with respect to said fluid transfer device; and amagnet moving apparatus including at least one magnet generating amagnetic field, said magnet moving apparatus being constructed andarranged to effect linear translation of said at least one magnetbetween an operational position with respect to the receptacle devicecarried in said receptacle carrier and a non-operational position withrespect to the receptacle device carried in said receptacle carrier,wherein said magnetic field of said at least one magnet draws themagnetically-responsive solid supports to an inner surface of thereceptacle device adjacent to said at least one magnet when said atleast one magnet is in said operational position, and wherein the effectof said magnetic field on said magnetically-responsive solid supports isless when said at least one magnet is in said non-operational positionthan when said at least one magnet is in said operational position, andwhen the receptacle device is positioned in the first position withrespect to the fluid transfer device, the receptacle device interfereswith translation of said magnet moving apparatus from saidnon-operational position to said operational position.
 11. The apparatusof claim 10, wherein said receptacle carrier is constructed and arrangedto impart an orbital motion to the receptacle device carried thereby.12. The apparatus of claim 10, wherein said fluid transfer devicefurther comprises a probe moving mechanism adapted to move the pluralityof probes in unison with respect to said receptacle carrier, and whereinsaid probe moving mechanism and said receptacle carrier are constructedand arranged so that movement of the plurality of probes with respect tothe receptacle carrier when the receptacle carrier is in the firstposition will cause the distal end of each probe to engage an associatedconduit carried on a receptacle device carried by the receptacle carrierso that a conduit becomes mounted on the distal end of each probe. 13.The apparatus of claim 12, wherein said magnet moving apparatuscomprises a plurality of stripping elements, each stripping elementbeing associated with a corresponding aspirator probe, and eachstripping element being adapted to remove a conduit from the distal endof the associated aspirator probe, wherein when said magnet movingapparatus is in the operational position, each stripping element is in aposition to engage the associated aspirator probe to strip the conduitmounted thereon, and when said magnet moving apparatus is in thenon-operational position, no stripping element is in a position toengage the associated aspirator probe to strip the conduit mountedthereon.
 14. The apparatus of claim 10, wherein said magnet movingapparatus comprises: a magnet carrier configured to carry said magnet; amotor; a threaded drive screw coupled to an output shaft of said motor;and a screw follower mounted to said magnet carrier, wherein said drivescrew is engaged with said screw follower such that powered rotation ofsaid drive screw by said motor causes translation of said magnetcarrier.
 15. The apparatus of claim 10, wherein said magnet movingapparatus comprises: a magnet carrier configured to carry said magnet; amotor with a drive pulley mounted to an output shaft thereof; an idlerpulley; and a drive belt carried on said drive pulley and said idlerpulley and coupled to said magnet carrier to transfer powered rotationof said drive pulley to translation of said magnet carrier.
 16. A methodfor removing a conduit from a distal end of each of a plurality of fluidtransfer probes, comprising: effecting powered linear translation of aslide in a direction transverse to the axes of the probes from a firstlocation to a second location, wherein when the slide is in the firstlocation, no portion of the slide is in a position to be engaged by anyof the probes, and when the slide is in the second location,conduit-stripping portions of the slide are in positions to be engagedby the distal ends of the probes; and effecting powered axial movementof the probes with respect to the slide to engage the distal ends of theprobes with the conduit-stripping portions of the slide and strip theconduits from the probes.
 17. The method of claim 16, wherein strippingthe conduits from the distal ends of the probes comprises moving theprobes in an axial direction toward the slide until the conduitsdisposed on the distal ends of the probes engage the conduit-strippingportions of the slide and then moving the probes in an opposite axialdirection away from the slide while retaining the conduits with theconduit-stripping portions of the slide to pull the conduits from thedistal ends of the probes.
 18. The method of claim 16, wherein retainingthe conduits with the conduit-stripping portions of the slide comprises:providing, for each conduit-stripping portion, a key-hole opening havinga first portion with a transverse size sufficient to permit the conduitto pass therethrough and a second portion with a transverse sizesufficient to permit the probe to pass therethrough, but not sufficientto permit the conduit to pass therethrough; passing the distal end ofthe probe with the conduit disposed thereon through the first portion ofthe key-hole opening; effecting a relative movement between the probeand the slide so that the probe is in the second portion of the key-holeopening; and withdrawing the probe from the key-hole opening, theconduit being retained by the conduit-stripping portion when the conduitis unable to pass through the second portion of the key-hole opening.19. The method of claim 18, comprising sequentially retaining each ofthe conduits during axial movement of the probes away from the slide sothat all conduits are not pulled from the distal ends of the probessimultaneously.
 20. The method of claim 16, further comprising mountingone or more magnets on the slide such that, when the slide is in thefirst location, the magnets have substantially no effect onmagnetically-responsive solid supports contained in a receptacle devicepositioned so as to be engageable by the probes, and when the slide isin the second location, the magnets are positioned adjacent to thereceptacle device so that the magnets will draw at least a portion ofthe magnetically-responsive solid supports to a wall of the receptacledevice.
 21. The method of claim 20, wherein the magnetically-responsivesolids supports are adapted to immobilize an analyte thereon.